1. Field of the Invention
The present invention relates to a manganese oxide material having MnO.sub.3 as a matrix, that exhibits current- and/or electrical field-induced insulator-to-metal transition and the accompanying antiferromagnetic-to-ferromagnetic transition and can advantageously be used as a switching device or memory device.
2. Description of the Prior Art
The discovery of high-temperature superconductivity in copper oxides has drawn attention to the spin-charge coupled dynamics of ozides of transition metals. In particular, considerable research is being conducted on perovskite type manganese oxide materials that exhibit negative colossal magnetoresistance. In the course of work on the design and development of related substances, research has been further stimulated by the discovery of the colossal magnetoresistance ("CMR") effect in which a type of charge ordered phase field fusion is manifested as a change of several magnitudes in electrical resistivity, and the discovery of field-induced antiferromagnatic insulator-to-ferromagnetic metal transitions that can be described as an extreme magnetoresistance effect. While there are known many perovskite type oxide materials that exhibit the CMR effect, such as Pr.sub.1-x Ca.sub.x MnO.sub.3, Pr.sub.1-x (Ca,Sr).sub.x MnO.sub.3 and Nd.sub.0.5 Sr.sub.0.5 MnO.sub.3, in each of these materials the CMR effect is controlled by an external magnetic field. This has made application to electronics-related fields difficult.
An object of the present invention is to provide a manganese oxide material exhibiting antiferromagnetic insulator-to-ferromagnetic metal transition that can be controlled by a current and/or electrical field.